Earth working involves the physical treatment of the earth and includes operations such as beating, compacting, crushing, cultivating, cutting, digging, furrowing, harrowing, leveling, mixing, plowing, pulverizing, rolling, scraping, scratching, smoothing, tilling, and so forth. For example, the earth is worked by an earth working tool driven by a vehicle (e.g., a tractor), and in other cases using hand tools (e.g., a hoe).